Directional hydraulic control valve



May 25, 1965 J. R. PLATE DIRECTIONAL HYDRAULIC CONTROL VALVE 2 Sheets-Sheet 1 Filed Dec. 3, 1962 1, 6 w 9 4 6 J y a 6 6 d1 g a J fl a Z 1 1 l w wfl m M/ 2 j nu May 25, 1965 J. R. PLATE 3,135,175

DIRECTIONAL HYDRAULIC CONTROL VALVE Filed Dec. 3, 1962 2 Sheets-Sheet 2 +76 73 )2, f .MPM mg United States Patent 3,185,175 DIRECTIONAL HYDRAULIC CONTROL VALVE John R. Plate, Milwaukee, Wis, assignor to Allis-Chalmers Manufacturing Company, Milwaukee, Wis. Filed Dec. 3, 1962, er. No. 241,702 Qlaims. (Cl. 137-59612) The invention relates to hydraulic control valves, and it is concerned more particularly with a particular valve for distributing the fluid output of two pumps so that a fluid motor, such as a single acting ram, may be selectively energized by either pump independently of the other.

The principal object of the invention is to provide an improved directional hydraulic valve of the mentioned character, and more particularly one which by simple axial adjustment of a single reciprocable valve spool will serve four purposes, namely: first, to trap operating fluid in a single acting hydraulic ram or the like; second, to admit pressure fluid from one of the pumps to the ram so as to energize the latter independently of fluid supply from the second pump; third, to admit pressure fluid to the ram solely from the second pump so as to energize the latter while the fluid supply of the first pump is diverted from the ram; and fourth, to disconnect both pumps from the ram and permit the latter to float.

Another object of the invention is to provide an improved hydraulic control valve of the mentioned character incorporating a high and a low resistance fluid passage through which pressure fluid may flow simultaneously from the second pump to the ram, the low resistance fluid passage being check valve controlled so as to prevent return flow of fluid through the low resistance passage.

The invention is primarily intended for use in hydraulic power lift systems for tractors, although its usefulness is not limited to such systems. In a typical tractor power lift system, such as disclosed for instance in US. Patent 2,679,199 issued on May 25, 1954 to W. F. Strehlow for Power Lift Means Affording Depth Regulation of Tractor Propelled Implements, raising and lowering of a tractor mounted plow or the like is accomplished hydraulically, that is, by means of a single acting hydraulic lifting ram and operating fluid pressurized by the power of the tractor motor. A common requirement of such a system is that the implement can be raised and lowered at the will of the operator, for instance, in case of a plow, at the end of a furrow and at the start of subject it to a limited amount of lifting power in order to transfer weight from the implement to the propelling wheels of the tractor when needed. Such weight transfer is commonly accomplished automatically by means of a draft sensing device which actuates a suitably constructed hydraulic control valve so that more or less weight will be transferred to the tractor propelling wheels by actuation of the lifting ram depending on the magnitude of the draft which is transmitted from the tractor to the implement.

A hydraulic control valve incorporating the present invention is particularly adapted to form a component part of a tractor power lift system for performing the above outlined various functions. Instead of one pump, as disclosed in the mentioned Strehlow patent, US. 2,679,199, two pumps, one of large capacity and the other of small capacity, will be provided in a power lift system incorporating the improved control valve of the present invention.

In such a system, a first predetermined position of axial adjustment of the valve spool will be a hold posi- Patented May 25, 1965 tion for sustaining the implement in an elevated posi tion, and in this condition of the system, the fluid output of both pumps will be diverted from the lifting ram.

A second predetermined position of axial adjustment of the valve spool will be a lift position, for raising the implement, and in this condition of the system the fluid output of the large pump will be delivered to the lifting ram independently of fluid delivery by the small pump.

A third predetermined position of axial adjustment of the valve spool will be a weight transfer position for increasing and decreasing the loading of the tractor drive wheels as needed. In this condition of the system, the fluid output of the large pump will be diverted from the lifting ram, and the fluid output of the small pump will be directed to or diverted from the lifting cylinder under the control of a draft sensing device.

A fourth predetermined position of axial adjustment of the valve spool will be a lowering position for letting the implement descend under its own weight from any raised position to which it has been adjusted. In this condition of the system, the fluid output of both pumps will be diverted from the lifting ram.

Referring to the accompanying drawings:

FIG. 1 is a diagrammatic view of a directional hydraulic valve and associated hydraulic circuit of a power lift and weight transfer system for tractors, the valve being shown in an implement hold position;

FIG. 2 is a detail view showing the directional valve of FIG. 1 in an implement lift position;

FIG. 3 is another detail view showing the directional valve of FIG. 1 in a weight transfer position; and

FIG. 4 is another detail view showing the directional valve of FIG. 1 in an implement lowering position.

The implement lift and weight transfer system which is diagrammatically outlined in FIG. 1 comprises, in general: a first fluid pump 1, a second fluid pump 2, a single acting lifting ram 3, a draft sensing device 4, a bypass valve 6 for the pump 2, a sump 7, and a spool type directional hydraulic valve 8.

The hydraulic valve 8 is an open center, four position, six connection, directional spool valve. It comprises a casing 9 which has a valve bore .11 and axially spaced radial enlargements thereof presenting, respectively, a first inlet chamber 12; a second inlet chamber 13; first and second exhaust chambers 14 and 16; a drain chamber 17 for seepage fluid; a delivery chamber 18; and first and second transfer chambers 19 and 21. The first inlet chamber 12 communicates with the fluid delivery side of the first pump 1 through an internal inlet passage and associated connecting line diagrammatically represented by the line 22. A second internal inlet passage of the valve casing 9 is generally indicated by the reference character 23 and has a primary branch 24 and a secondary branch 26. The primary branch 24 includes a bore 27 of a check valve plug 28, and it is connected with the transfer chambers 19 and 21 through a U-shaped passage 29, and with'the first inlet chamber 12 through a passage 31. The junction of the U-shaped passage 29 with the passage 3-1 is controlled by a plunger type check valve 32 which is spring biased into the position shown in FIG. 1 so as to prevent fluid flow from the U-shaped passage 29 into the first inlet chamber 12, and which yields to pressure created in the first inlet chamber 12 by the pump 1. The plunger of the valve 32 has a hollow stem with radial holes 33 which connect the U-shaped passage 29 in fluid communicating relation with the bore of the check valve plug 28. The stem of the check valve 32 may have radial play within the bore of the plug 28, and fluid may leak from the passage 29 into the bore of the plug 28 even when the check valve 32 opens fully as shown in FIG. 2.

The check valve plug 28 contains a ball type check valve 34, and a coil spring36 reacts between the ball of valve 34 and the plunger of valve 32. The ball of valve 34 is seated on an internal shoulder of the plug 28 so as to prevent return flow of fluid through the primary branch 24 of the scond inlet passage 23 into the secondary branch 26 and second inlet chamber 13. Fluid delivered from the second pump 2 may flow into the second inlet passage 23 of the valve 8 through connecting lines 37, 38 when the bypass valve 6 is closed, as will be explained more fully hereinbelow.

The secondary branch 26 of the second inlet passage 23 has a restriction 71 at its junction with the second inlet chamber 13 so as to provide a high resistance passage from the delivery side of the pump 2 into the second inlet chamber 13. On the other hand, the primary branch 24 of the second inlet passage 23 and the bores 27 and 33 provide a low resistance passage from the delivery side of the pump 2 into the U-shaped passage 29 of the valve body 9. This low resistance passage is controlled by the ball type check valve 34, so as to prevent return flow of fluid through the primary branch 24.

Reciprocably mounted in the bore 11 of the valve casing 9 is a valve spool 41 which is selectively adjustable to any of the four positions in which it is shown in FIGS. 1, 2, 3, and 4, respectvely. A manually operable lever 42 for effecting such adjustment of the valve spool is diagrammatically indicated in the drawings. As shown, the lever 42 is pivotally mounted on a stationary bracket 43 connected with'the valve casing 9, and rocking of the lever 42 is transmitted to the. valve spool 41 by a pin and slot connection 44.

The spool 41 of the valve 8 has a first land 46 which is operative to control fluid passage between the first inlet chamber 12 and the first exhaust chamber 14 as illustrated by FIGS. 1 and 2, and which is also operative to control fluid passage between the first transfer chamber 19 and the delivery chamber 18 as illustrated by FIGS. 3 and 4.

A second land 47 of the valve spool 41 is operative to control fluid passage between the second inlet chamber 13 and the second transfer chamber 21 as illustrated by FIGS. 2 and 3.

A third land 48 of the valve spool 41 is operative to control fluid passage between the second inlet chamber 13 and the second transfer chamber 21 as illustrated by FIGS. 3 and 4.

A fourth land 49 of the valve spool 41 is operative to control fluid passage between the delivery chamber 18 and the second exhaust chamber 16, as illustrated by FIGS. 3 and 4.

In the hold position of the valve 8 as shown'in FIG. 1, the spool 41 occupies a first axially adjusted position in which the land 46 establishes communication between inlet chamber 12 and exhaust chamber 14, and between first transfer chamber 19 and delivery chamber 18. The land 47 disconnects second inlet chamber 13 from second transfer chamber 21. The land 48 is ineffective, and the land 49 disconnects the delivery chamber 18 from the second exhaust chamber 16. Upon adjustment of the spool 41 to the first position as shown in FIG. 1 fluid from the first inlet passage 22 will be diverted from the delivery chamber 18 and fluid from the second inlet passage 23 will be permitted to flow into the delivery chamber 18 while the latter is disconnected from the second exhaust chamber 16.

In the lift position of valve 8 as shown in FIG. 2, the spool 41 occupies a second axially adjusted position in which the land 46 disconnects inlet chamber 12 from first exhaust chamber 14, and connects first transfer chamber 19 with delivery chamber 18. The land 47 disconnects second inlet chamber 13 from second transfer chamber 21; the land 48 is ineflective, and the land 49 disconnects delivery chamber 18 from second exhaust chamber 16. Upon adjustment of the spool 41 to .the second position shown in FIG. 2 fluid from the first and second inlet passages 22 and 23 will be permitted to flow into the delivery chamber 1 8 while the latter is disconnected from the second exhaust chamber 16.

In the Weight transfer position of valve 8 as shown in FIG. 3, the spool 41 occupies a third axially adjusted position in which the land46 establishes communication between inlet chamber 12 and first exhaust chamber 14, and between first transfer chamber 19 and delivery chamber 18. The land 47 establishes communication between the second inlet chamber 13 and second transfer chan1- ber 21. The land 48 is ineflective, and the land 49 disconnects delivery chamber 18 from second exhaust chamber 16. Upon adjustment of the spool 41 to the third position shown in FIG. 3 fluidfrom the first inlet passage 22 will be diverted from," and fluid from the second inlet passage 23 will be directed into the delivery chamber 18 while the latter is disconnected from the second exhaust chamber 16.-

A centering mechanism 51 for the spool 41 of the valve 8 comprises a coil spring 52 and thrust cups 53 and 54 which cooperate with a stem portion 56 of the valve spool 41 to yieldingly retain the spool in the centered position in which it is shown in FIG. 1 Shifting movement of the valve spool in either direction from its center position is yieldingly opposed by the spring 52 in conventional manner.

A detent mechanism 57 for the valve spool 41 comprises two detent balls 58, 59 which are caged in the tubular end of the valve stem 56 and are biased radially outward by a backing ball 61 and a coil spring 62. 'A stationary guide sleeve 63 for the balls 58 and 59 is mounted on-the valve casing 9 and presents an internal cylindrical wall 64 at the outer end of the sleeve 63, and another internal cylindrical wall 66 extending axially from the inner end of the wall 64. The wall 66 has a smaller diameter than the wall 64, and at the junction of the walls 64, 66 the sleeve 63 presents a concave shoulder 67. As shown in FIG. 3, the internal shoulder 67 of the sleeve 63 is engageable by the balls 58, 59 to releasably retain the valve spool 41 against axial displacement by the centering spring 52 after the spool has been moved from the hold position shown in FIG. 1 to the weight transfer position shown in FIG. 3 by manipulation of the hand lever 42. The spool 41 can therefore be adjusted to occupy either the hold position shown in FIG. 1 or the Weight transfer position shown in FIG. 3 and remain in either of said positions without being held there manually by means of the lever 42. The spool will automatically return from the lift position of FIG. 2 to the hold position shown in FIG. 1 when the operator releases his hold on the hand lever 42. Similarly, the spool 41 will automatically return from the lowering position shown in FIG. 4 to the weight transfer-position shown in FIG. 3 when the hand lever 42 is released. Return of the valve spool 41 from the weight transfer position shown in FIG. 3 to the hold position shown in FIG. 1 may be effected by application of manual power to the hand lever 42 so as to overcome the restraint which is exerted against such movement by the coaction of the balls 58, 59 with the shoulder 67 under the pressure of the spring 62.

The valve body 9 has a delivery passage 68 in communication with the delivery chamber 18, and the outer end of the delivery passage 68 is tapped, as is the outer end of the second inlet passage 23, for connection with a hose line or the like. The exhaust chambers 14 and 16 and the drain chamber 17 are preferably interconnected within the valve casing 9 but for clarification such internal interconnection of the chambers 14, 16 and 17 is diagrammatically indicated in FIG. 1 by lines 14', 16' and 17 and a sump line 69.

In the power lift and weight transfer system as shown in FIG; 1, the first inlet passage 22 of the valve casing 9 is connected to the outlet side of the pump 1, and the suction side of the pump is connected with the sump line 69. The second inlet passage 23 of the casing 9 is connected by lines 37, 38 with the outlet side of pump 2 and also with an inlet passage 70 of bypass valve 6. An exhaust line 72 connects the outlet of valve 6 with the sump 7. The delivery passage 68 of the valve casing 9 is connected with the ram 3 by a'hose or pipe line 73. The rear part of a tractor on which the ram 3 and associated implement lift arm 74 are mounted is shown in FIG. 1 by dash dotted line, and an implement draft tongue 77 is connected with the lift arm 74 and with the draft sensing device 4 in conventional manner. The draft sensing device is connected with a reciprocable valve spool 78 of valve 6, and the valve 6 also includes a relief valve 79.

FIG. 1 shows the bypass valve 6 in an open condition which permits passage of fluid from the pump 2 through the valve 6 back to sump without appreciable resistance. In operation of the tractor, the bypass valve remains open as long as the draft transmitted through the draft bar 77 does not exceed a predetermined limit. However, when the draft exceeds that limit, the bypass valve is closed by operation of the draft sensing device 4, and as a result the fluid discharge from the pump 2 will be forced into valve 8 through connecting line 38 and, depending on the condition of the valve 8 as more fully explained hereinbelow, will become effective to transfer .implement wei ht to the tractor drive wheels. When the draft force returns to or falls below the predetermined limit, the draft sensing device automatically causes the valve 6 to open, thereby restoring the pump 2 to idling condition and permitting pressure fluid from the ram 3 to return to sump 7 through lines 38 and 72. y

In the hold position of the valve 8 as shown in FIG.

1, pressure fluid is trapped in the ram 3 by lands 47, 46,

49, and by check valves 32 and 34 Pump 1, which preferably has larger output capacity than pump 2, idles, and the small capacity pump 2 could feed into the ram 3 through the ball check valve 34 if bypass valve 6 were closed. However, the valve 8 is normally placed into the hold position only after the implement draft tongue 77 has been raised, and in the absence of draft on the tongue, bypass valve 6 is open and pump 2 idles the same as pump 1.

In the lift position of valve 8 as shown in FIG. 2, pressure fluid from pump 1 passes through check valve 32, passage 29, first transfer chamber 19, delivery chamber 18, passage 68 and line 73 into the expansion chamber of ram 3. The small capacity pump 2 could feed into the ram 3 through the ball check valve 34 but will do so only if bypass valve 6 should be closed, for instance manually. In that case both pumps 1 and 2 would feed pressure fluid jointly into the ram 3.

In the weight transfer position of valve 8 as shown in FIG. 3, the land 46 establishes communication be tween inlet chamber 12 and first exhaust chamber 14, and the large capacity pump 1 idles, consuming negligible power. The small pump 2 likewise idles as long as the bypass valve 6 is open.

If an implement, such as a plow, not shown, is advanced in working position by the tractor and the valve 8 is in the weight transfer position, the sensing device 4 will alternately close and open the bypass valve 6, depending on draft conditions. When the draft exceeds a predetermined limit the valve 6 closes and the small pump will feed pressure fluid into the ram 3 through lines 37, 38, branch 24 of passage 23, bore 27 of plug 28, radial bores 33, passage 29, chambers 19, 18; passage 68 and line 73. As a result of such pressure fluid delivery from the small capacity pump 2 into the lifting ram 3, while the implement is advanced in working position, some of the weight of the implement and from the tractor front wheels will be transferred to the tractor rear driving wheels. The additional weight thus imposed upon the tractor drive wheels will improve the ability of the tractor to pull a heavy load without wheel slippage.

.Closing and opening of the bypass valve 6 is effected by relatively short back and forth movements of the valve spool 78. Upon closing of the valve 6 while the valve 8 is in the weight transfer position shown in FIG. 3, practically all of the oil delivered from the pump 2 will flow through the low resistance primary branch 24, 27 and through radial bores 33 of the check valve plunger 32. Some oil delivered by the pump 2 will also flow into the U-shaped passage 29 through the high resistance passage afforded by branch 26 and restriction 71. This oil flow through the high resistance passage and chambers 13, 21, however, will be small as compared with the oil flow through the low resistance passage 24, 27, 29 and chambers 19, 18. Accordingly, application of lifting power to the implement draft bar 77 will be instantaneous when the draft sensing device calls for weight transfer from the implement to the t The first pump 1 does not participate in such tractor. Weight transfer. It continues to idle during weight transfer, unless it is called upon to perform other functions.

When a heavy draft condition which has caused weight transfer from the implement to the tractor subsides, it is desirable for reasons of economical tractor operation, that the tractor wheels be relieved of the additional weight which has been transferred to them by operation of the small capacity pump 2 and lift ram 3. More particularly, in the interest of satisfactory implement performance, the restoration of Weight from the tractor to the implement should be gradual and not sudden as the weight transfer from the implement to the tractor. This desirable result is accomplished by the provision of the restriction 71 at the junction of the branch 26 with the second inlet chamber 13. When the bypass valve 6 opens due to draft decrease while the valve 8 is in the weight transfer position, pressure fluid from the ram 3 may return to sump through line 73, passage 68, chambers 18, 19, passage 29, chambers 21, 13, restriction 71, branch 26 of passage 23, line 38, open valve 6, and exhaust line 72. Return flow through the low resistance passage 29, 27, 24 is prevented by ball check valve 34.

The size of the restriction 71 is such that any lifting force of arm 74 effective while the bypass valve 6 is closed will vanish gradually when the bypass valve 6 is opened by operation of the draft sensing device 4.

When the valve 8 is in the weight transfer position as shown in FIG. 3, the small capacity pump 2 is operable to deliver pressure fluid to the lifting ram 3 independently of the large capacity pump 1.

In the lowering position of the valve 8 as shown in FIG. 4, the pressure fluid may return rapidly from the ram 3 to sump through line 73, passage 68, chambers 18, 16, exhaust line 16 and sump line 69. The large capacity pump 1 feeds back to sump through chambers 12, 14, exhaust line 14' and sump line 69, unless called upon to perform other functions. The first land 46 will be operative to connect the first inlet chamber 12 with the first exhaust chamber 14; the second land 47 will be inoperative, and the third land 48 will be operative to disconnect the second inlet chamber 13 from the second transfer chamber 21; and the fourth land 49 will be operative to connect the delivery chamber 18 with the second exhaust chamber 16. As a result, fluid from the first and second inlet passages 22 and 23 will be prevented from flowing into the delivery chamber 18 While the latter is connected with the second exhaust passage 16'. The small capacity pump 2 will feed back to sump through line 37, open valve 6 and exhaust line 72, assuming that the tractor is standing still and no draft is transmitted through the draft sensing device 4. Should for any reason the valve 6 be closed while the valve 8 is in the lowering position, the fluid discharge of the pump 2 will return to sump through relief valve 79 of valve 6.

It should be understood that it is not intended to limit the invention to the specific details herein shown and described for purposes of illustration, as various modifications within the scope of the appended claims may occur to persons skilled in the art.

Having now particularly described and ascertained the nature of my said invention and the manner in which it is to be performed, I declare that what I claim is:

1. A directional hydraulic valve comprising, a casing having a valve bore and axially spaced radial enlargements thereof presenting, respectively, a first and second inlet chamber, a first and a second transfer chamber, a first anda second exhaust chamber, and a delivery chamber; internal passage means presenting a first inlet passage connected with said first inlet chamber; a second inlet passage having a primary branch connected with said first inlet chamber and with said first and second transfer chambers, and a secondary branch connected with said second inlet chamber, check valve means positioned within said primary branch and coacting therewith for preventing return flow of fluid therethrough to said second inlet passage and fluid flow from said primary branch into said first inlet chamber, and a valve spool in said valve bore and provided with axially spaced apart lands and said lands being cooperable with said bore so as to selectively direct fluid flow from said first inlet chamber and delivery chamber to said first and second exhaust chambers, respectively; and to selectively direct fluid flow from said first and second inlet chambers either jointly or separately to said delivery chamber; said lands including a first land operative to control fluid passage from said first inlet chamber to said first exhaust chamber, and to control fluid flow from said first transfer chamber to said delivery chamber; second and third lands operative alternately to control fluid passage between said second inlet chamber and said second transfer chamber; and a fourth land operative to control fluid passage between saiddelivery chamber and said second exhaust chamber.

2. A directional hydraulic control valve as set forth in claim 1, wherein said lands of said valve spool are arranged thereon so that upon movement of the latter to a first axially adjusted position relative to said bore, said first land will be positioned to connect said first inlet chamber with said first exhaust chamber; said second land will be positioned and said third land will be inoperative to disconnect said second inlet chamber from said second transfer chamber; and said fourth land will be positioned to disconnect said delivery chamber from said second exhaust chamber, whereby fluid from said first inlet passage will be diverted from said delivery chamber and fluid from said second delivery chamber will be permitted to flow into said delivery chamber while the latter is disconnected from said second exhaust chamher.

3. A directional hydraulic control Valve as set forth in claim 2 wherein said lands of said valve spool are arranged thereon so that upon movement of the latter from said first to a second axially adjusted position relative to said bore, said first land will be positioned to disconnect said first inlet chamber from said first exhaust chamber; said second land will be positioned to disconnect said first inlet chamber from said first exhaust chamber; said second land will be positioned and said third land will be inoperative to disconnect said inlet chamber from said second transfer chamber; and said fourth land will be positioned to disconnect said delivery chamber from said second exhaust chamber, whereby fluid from said first and second inlet passages will be permitted to flow into said delivery chamber while the latter is disconnected from said second exhaust chamber.

4. A directional hydraulic control valve as set forth in claim 2, wherein said secondary branch of said second inlet passage being restricted so as to provide a higher resistance to fluid flow therethrough than said primary branch, and wherein said lands are further arranged on said valve spool so that upon movement of the latter from said first to a third axially adjusted position relative to said bore said first land will be positioned to connect said first inlet chamber with said first exhaust chamber; said second and third lands will be positioned to connect said second inlet chamber with said second transfer chamber; and said fourth land will be positioned to disconnect said delivery chamber from said second exhaust chamber, whereby fluid from said first inlet passagewill be diverted from, and fluid from said second inlet passage will be directed into said delivery cham her while the latter is disconnected from said second exhaust chamber,

5. A directional hydraulic control valve as set'forth in claim 4 wherein said lands of said valve spool are further arranged thereon so that upon movement of the latter from said third to a fourth axially adjustedposi- .tion relative to said bore said first land will be positioned to connect said first inlet chamber with said first exhaust chamber; said second land will be inoperative and said third land will be positioned to disconnect said second inlet chamber from said second transfer chamber; and said fourth land will be positioned to connect said delivery chamber with said second exhaust chamber, whereby fluid from said first and second inlet passages will be prevented from flowing into said delivery chamber While the latter is connected with said exhaust passage.

References Cited by the Examiner UNITED STATES PATENTS 1,982,711 12/34 Vickers 52 2,846,848 8/58 Coker 9129 X 2,904,957 9/59 Quayle 91--3l X 2,946,144 7/60 Anderson 6052 X 3,064,426 11/62 Furia et a]. 9128 M. CARY NELSON, Primary Examiner.

HENRY T. KLINKSIEK, Examiner. 

1. A DIRECTIONAL HYDRAULIC VALVE COMPRISING, A CASING HAVING A VALVE BORE AND AXIALLY SPACED RADIAL ENLARGEMENTS THEREOF PRESENTING, RESPECTIVELY, A FIRST AND SECOND INLET CHAMBER, A FIRST AND A SECOND TRANSFER CHAMBER, A FIRST AND A SECOND EXHAUST CHAMBER, AND A DELIVERY CHAMBER; INTEGRAL PASSAGE MEANS PRESENTING A FIRST INLET PASSAGE CONNECTED WITH SAID FIRST INLET CHAMBER; A SECOND INLET PASSAGE HAVING A PRIMARY BRANCH CONNECTED WITH SAID FIRST INLET CHAMBER AND WITH SAID FIRST AND SECOND TRANSFER, CHAMBERS, AND A SECONDARY BRANCH CONNECTED WITH SAID SECOND INLET CHAMBER, CHECK VALVE MEANS POSITIONED WITHIN SAID PRIMARY BRANCH AND COACTING THEREWITH FOR PREVENTING RETURN FLOW OF FLUID THERETHROUGH TO SAID SECOND INLET PASSAGE AND FLUID FLOW FROM SAID PRIMARY BRANCH INTO SAID FIRST INLET CHAMBER, AND A VALVE SPOOL IN SAID VALVE BORE AND PROVIDED WITH AXIALLY SPACED APART LANDS AND SAID LANDS BEING COOPERABLE WITH SAID BORE SO AS TO SELECTIVELY DIRECTED FLUID FLOW FROM SAID FIRST INLET CHAMBER AND DELIVERY CHAMBER TO SAID FIRST AND SECOND EXHAUST CHAMBERS, RESPECTIVELY; AND TO SELECTIVELY DIRECT FLUID FLOW FROM SAID FIRST AND SECOND INLET CHAMBER EITHER JOINTLY OR SEPARATELY TO SAID DELIVERY CHAMBER; SAID LANDS INCLUDING A FIRST INLET CHAMBER TO SAID FIRST FLUID PASSAGE FROM SAID FIRST INLET CHAMBER TO SAID FIRST EXHAUST CHAMBER, AND TO CONTROL FLUID FLOW FROM SAID FIRST TRANSFER CHAMBER TO SAID DELIVERY CHAMBER; SECOND AND THIRD LANDS OPERATIVE ALTENATELY TO CONTROL FLUID PASSAGE BETWEEN SAID SECOND INLET CHAMBER AND SAID SECOND TRANSFER CHAMBER; AND A FOURTH LAND OPERATIVE TO CONTROL FLUID PASSAGE BETWEEN SAID DELIVERY CHAMBER AND SAID SECOND EXHAUST CHAMBER. 